Automatic hydraulic buffer



Sept. 15, 1964 A. SMYKLO ETAL AUTOMATIC HYDRAULIC BUFFER Filed March 23,1962 r 2 Sheets-Sheet l INVENTORS ALEXANDER SMYKLO GEORGE B. SCHIL ROTHATTORNE S p 15, 1954 A. SMYKLO ETAL 3,148,707

AUTOMATIC HYDRAULIC BUFFER Filed March 23, 1962 2 Sheefs-Sheet 2 UnitedStates Patent 3,148,707 AUTOMATHI HYDRAULIC BUFFER Alexander Smyklo,Union City, Calif., and George B.

Schiidroth, Manchester, N.H., assignors to the United States of Americaas represented by the Secretary of the Air Force Filed Mar. 23, 1962,Ser. No. 182,148 2 Claims. (Cl. 138-31) This invention relates tohydraulic apparatus and, more specifically, to an accumulator or bufferused on such apparatus.

Many installations of hydralic apparatus of various types includehydraulic pumps to supply high pressure fluid for driving varioushydraulic motors and actuating devices. On much apparatus of this typeit is practically impossible to balance the output of the pumps to thevariable demands of the motors or other fluid powered devices. A commonmeans for absorbing surplus fluid when the pump output momentarilyexceeds demand, and for supplying needed fluid when demand momentarilyexceeds pump output is to place an accumulator or butter into thehydraulic conduit between the pump and the fluid using devices. Suchaccumulator or buffer is normally T connected to the fluid carryingconduit.

A buffer, of the type to which this invention pertains, may have afloating piston in a cylinder. That portion of the cylinder on one sideof the piston is in communication with the hydraulic fluid, and thatportion of the cylinder on the opposite side of the piston is chargedwith a gas at a pressure comparable to the normal operating pressure ofthe hydraulic system. It is thus noted that when pump output momentarilyexceeds demand, the surplus fluid will be absorbed into the hydraulicend of the butter cylinder while moving the floating piston and furthercompressing the gas. During the subsequent operation of the apparatus,the gas in the buffer which became compressed to an above normalpressure will tend to purge the buffer of surplus fluid in order to produce a pressure balance between the gas side and the hydralic side ofthe floating piston within the buffer.

In like manner, when demand momentarily exceeds pump output and there isa drop in hydraulic pressure, the entrapped gas, which is now at ahigher pressure than hydraulic line pressure, will move the floatingpiston and thereby supply needed fluid to the fluid using devices.During the subsequent operation of the apparatus, hydraulic fluid willre-enter the buffer until there is a pressure balance on the floatingpiston. It is necessary to provide seal rings on the piston to preventan interchange of fluid and gas.

Little difficulty is encountered in preventing ring leakage duringnormal operation sincethere is little, if any, pressure differentialacross the rings. However, when the apparatus is shut down an thehydraulic pressure decays, the pressure differential across the ringsand resultant leakage of gas into the hydraulic system becomes a severeproblem.

It is, accordingly, the primary object of this invention to provide ameans for preventing the escape of the gas in a gas charged buffer intothe hydraulic system of a hydraulic apparatus during shut-down.

It is another object of this invention to provide a means for reducingthe pressure differential across the seal rings on the floating pistonof a hydraulic buffer during shutdown in order to prolong ring life.

It is a further object of this invention to provide a valve means forpreventing the entire escape of the fluid Within a hydraulic buffer.

It is yet another object of this invention to provide a means foraccomplishing the above objectives without interference with a normaloperation of the buffer.

Additional objects, advantages and features of the invention reside inthe construction, arrangement and combination of parts involved in theembodiment of the invention as will appear from the followingdescription and accompanying drawings, wherein:

FIG. 1 is a schematic drawing of the hydraulic buffer T connected at oneend to a hydraulic fluid conduit and connected at the other end to asource of high pressure FIG. 2 is a partial section of the body memberand piston, and showing the valve plug against its seat to entraphydraulic fluid during shut-down; and

FIG. 3 is a partial section similar to FIG. 2 and showing thearrangement of the elements during normal operation of the hydraulicapparatus.

Referring to FIG. 1, the buffer referred to generally as 14) has ahousing or body member 11 containing a closed end cylinder 12, whichhouses a free floating piston 14 adapted for dividing the cylinder intotwo end chambers 13 and 15. Chamber 13 is adapted for use as a highpressure air or gas chamber, and chamber 15 is adapted for use as ahydraulic fluid chamber. The piston is provided with ring sealing meansfor preventing the leakage of fluid or gas from one end chamber into theother, while at the same time permitting axial movement of the piston.The sealing means consists of a continuous O ring 16 and an 0 ring 18which is served to provide a small gap 20 for a purpose to behereinafter described. Both rings 16 and 18 are preferably neoprene orsimilar nonmetallic ductile material. The chamber 15, which forms thehydraulic end of buffer 10, has an orifice 23 which is T connected tohydraulic fluid conduit 22 by means of conduit 24. It is presumed thatconduit 22 is carrying hydraulic fluid from a pump not shown to ahydraulic motor not shown and that the fluid flow is in the directionindicated by the arrows. The opposite, or gas chamber 13 end of cylinder12 has a closed end containing an orifice 27 which is connected to asource of high pressure gas or air 26 by means of conduit 28. It isnoted on FIG. 1 that the gas pressure is always acting against piston14, and that the hydraulic fluid is free toenter or leave chamber 15,the direction of flow being dependent upon whether or not the hydraulicfluid pressure is greater or less than the pressure of the gas. A staticflow condition exists when there is a pressure balance across thepiston.

Referring more specifically to FIG. 3, the housing or body member 11 maybe made of pipe or tubing having one end closed by Welded or threadedmeans to provide a closed end. Or, body member 11 may be made of acasting having an integrally closed end, or a closed end which is boltedin place or otherwise joined in various manners well known to the art.The hydraulic end of cylinder 12 is openably closed with an end memberor plug 30 having external threads 32 which engage correspondinginternal threads in cylinder 12. A valve seat 34 having an externallythreaded shank 36 engages a correspondingly threaded bore in end member30. The internal end of valve seat 34, which also provides orifice 23,has a spherical seat faced with a facing 3%. Facing 38 may be made ofsoft ductile metal such as copper, aluminum or gold; or of plastic, andmay be joined to valve seat 34 invarious manners well known to the art.The use of a facing such as facing 38 is not absolutely necessary, butis desirable under certain conditions to assure a readily obtainableleak-proof closure upon shut-down. A plurality of bosses 46 project fromthe inner face of end plug 30. The bosses are of uniform height andlimit the movement of the piston during shut-down in a manner and for apurpose to be hereinafter explained. If desired, other means such as anintegral ring joined to end plug 34, or a plurality of pins may besubstituted for bosses 40. Likewise, the piston travel limiting meansmay be on the piston itself, rather than on the end plug. Sealing meanswell known to the art may be provided to prevent the escape of hydraulicfluid. The buffer 1% may be joined to the hydraulic system by means of atubing connection, a manifold, or any desired method, such method ofjoining not constituting a part of this invention.

The hydraulic end face of piston 14 contains a threaded counterborewhich is coaxial with valve seat 34 and which threadably receivesretainer cup 42. A ball of valve plug 44, of steel or other suitablematerial, has joined thereto a rod or stem 46. A suitable compressionspring 4-8 is brazed or otherwise joined to a face of washer 50.

Ball 44 with attached stem 4-6, compressionspring 48 with attachedwasher 5t? and retainer cup 42 are assembled into a sub-assembly byplacing the free end of the spring onto the ball in such manner thatstem 46 passes through a bore in washer 5i Washer 56 is received withinbore 52 of retainer cup 4-2 while stem 46 passes through bore 54 in theend of cup 42 where it is retained by retainer washer 56 which isriveted or otherwise joined to the free end of stem 46. After washer 56is joined to stem 46, the ball or valve plug 44 is slidably retained foraxial movement within cup 42 and biased outwardly by compression spring48. The sub-assembly is threadably joined to the hydraulic end of piston14 by means of a pin spanner wrench engaging holes 58 in retainer cup42. Retainer washer 56 moves axially within counterbore 66 when ball 44moved against spring 4%. Although the valve plug used in the embodimentof the invention shown and described was a ball, the plug could be madein other forms such as conical or elliptical.

During operation of the hydraulic apparatus to which the buiier isjoined, the floating piston assumes a position as shown on FIG. 1 andH6. 3. During shut-down, the floating piston will assume a position asshown on FIG. 2 with the ball 44 engaging valve seat 34. As shown onFIG. 3, a portion of the hydraulic fluid is entrapped in the butter. Theentrapped fluid will be at the same pressure as the gas acting on theother side of the piston. Gap 2% in ring 18 permits the area between theseal rings to assume the same unit pressure as that of the chambers ateach end of the piston, with a resulting zero pressure differentialacross the rings. pressure across the rings assures long ring life.Bosses 49 on end plug 3% are a protective means, in case of leakageduring shut-down, for preventing sufficient piston travel to cause thevalve plug on the seat to support the entire force of the applied gas onthe other side of the piston, and thereby damage the valve mechanism.

It is noted that the bosses 40 may be eliminated by making cup 42 ofgreater depth, thereby permitting further movement of ball 44 into thecup, in order that the face of the piston will engage the inner face ofend plug 36 before the plug reaches the inner limit of its permissibleaxial movement.

It is further noted that the amount of fluid entrapped on shut-down willbe determined by the length of stem 46 which controls the position ofthe piston at the time the ball plug engages its seat.

If desired, valve seat 34 may be installed into the closed end ofhousing 11, in which case the open end of the cylinder would become thegas end. When such arrangement is used, piston travel limiting meanssuch as bosses 46 may be attached to the end of the piston.

It is to be understood that the embodiment of the present invention asshown and described is to be regarded as illustrative only and that theinvention is susceptible to variations, modifications and changes withinthe scope of the appended claims.

We claim:

1. A hydraulic buffer comprising: a body member, an open end cylinderwithin said body member, an end member for openably closing the open endof said cylinder, a floating piston within said cylinder, said pistonbeing axially movable within said cylinder and adapted for dividing saidcylinder into opposing end chambers, sealing means on said piston, saidsealing means comprising a plurality of ductile non-metallic ringsadapted to prevent leakage from one of said chambers into the opposing Ychamber, an orifice communicating with each end of said The zerodifferential cylinder, at least one of said orifices being coaxial withsaid cylinder and passing through said end member, a valve seatcommunicating with said coaxial orifice, and a valve plug subassemblycoaxial with said cylinder and said valve seat, and comprising aretainer cup having external threads engaging a threaded counterbore inthe end of said piston with the bottom of the retainer cup against thebottom of the counterbore, a ball valve plug, a stem joined to said ballvalve plug and slidably passing through the bottom of said retainer cup,means joined to said stem for retaining said stem in said retainer cup,and a compression spring disposed over said stem and nesting on saidball valve plug to axially bias said ball valve plug from the face ofsaid piston.

2. A hydraulic buffer comprising: a body member, an open end cylinderwithin said body member, an end member for openably closing the open endof said cylinder, a floating piston within said cylinder, said pistonbeing axially movable within said cylinder and adapted for dividing saidcylinder into opposing end chambers, sealing means on said piston, saidsealing means comprising two ductile nonmetallic rings adapted toprevent leak age from one of said chambers into the opposing chambers,one of said rings being severed to provide a small gap permitting thearea between the rings to communicate with one of said chambers, anorifice communicating with each end of said cylinder, at least one ofsaid orifices being coaxial with said cylinder and passing through saidend member, a valve seat communicating with said coaxial orifice, and avalve plug subassembly coaxial with said cylinder and said valve seat,and comprising a retainer cup having external threads engaging athreaded counterbore in the end of said piston with the bottom of theretainer cup against the bottom of the counterbore, a ball valve plug, astem joined to said ball valve plug and slidably passing through thebottom of said retainer cup, means joined to the end of said stem forretaining said stem in said retainer cup, a Washer axially passing oversaid stem and resting against the bottom of said retainer cup, and acompression spring disposed over said stem with one end joined to saidwasher and the other end nesting on said ball valve plug to axially biassaid ball valve plug from the face of said piston.

References Cited in the file of this patent UNITED STATES PATENTS

1. A HYDRAULIC BUFFER COMPRISING: A BODY MEMBER, AN OPEN END CYLINDERWITHIN SAID BODY MEMBER, AN END MEMBER FOR OPENABLY CLOSING THE OPEN ENDOF SAID CYLINDER, A FLOATING PISTON WITHIN SAID CYLINDER, SAID PISTONBEING AXIALLY MOVABLE WITHIN SAID CYLINDER AND ADAPTED FOR DIVIDING SAIDCYLINDER INTO OPPOSING END CHAMBERS, SEALING MEANS ON SAID PISTON, SAIDSEALING MEANS COMPRISING A PLURALITY OF DUCTILE NON-METALLIC RINGSADAPTED TO PREVENT LEAKAGE FROM ONE OF SAID CHAMBERS INTO THE OPPOSINGCHAMBER, AN ORIFICE COMMUNICATING WITH EACH END OF SAID CYLINDER; ATLEAST ONE OF SAID ORIFICES BEING COAXIAL WITH SAID CYLINDER AND PASSINGTHROUGH SAID END MEMBER, A VALVE SEAT COMMUNICATING WITH SAID COAXIALORIFICE, AND A VALVE PLUG SUBASSEMBLY COAXIAL WITH SAID CYLINDER ANDSAID VALVE SEAT, AND COMPRISING A RETAINER CUP HAVING EXTERNAL THREADSENGAGING A THREADED COUNTERBORE IN THE END OF SAID PISTON WITH THEBOTTOM OF THE RETAINER CUP AGAINST THE BOTTOM OF THE COUNTERBORE, A BALLVALVE PLUG, A STEM JOINED TO SAID BALL VALVE PLUG AND SLIDABLY PASSINGTHROUGH THE BOTTOM OF SAID RETAINER CUP, MEANS JOINED TO SAID STEM FORRETAINING SAID STEM IN SAID RETAINER CUP, AND A COMPRESSION SPRINGDISPOSED OVER SAID STEM AND NESTING ON SAID BALL VALVE PLUG TO AXIALLYBIAS SAID BALL VALVE PLUG FROM THE FACE OF SAID PISTON.